When we develop we have a tendency to name strings something which will make them recognizable - such as “isUserLogged” or “username,” however, when building a large application, in the end this practice contributes to the size of the app significantly.
The best practice:
Create a separate document where you give each string and variable a recognizable name as an identifier, and an actual name for use in the app. Keep the strings limited to one letter or at the most one letter and one number.
Also, make a column so you can note each activity and flow function where the variable is used, so you can reference it for debugging purposes.
If you ever look at a well written sdk, you will see this is what they do.
I recently went through an entire app and did this. In the end, an app with a 34 MB download size was reduced to 5.8 MB.
I had a lot of variables.